Electronic device with equalization, integrated circuit and methods therefor

ABSTRACT

An electronic device for a wireless communication system is described. The electronic device comprises: a receiver configured to receive a modulated signal on a communication channel; and a processor, coupled to the receiver and configured to: process the received modulated signal; identify a communication channel characteristic based on the processed received modulated signal; select an equalizer having a first set of equalization coefficients based on the identified communication channel characteristic, wherein the first set of equalization coefficients is selected from a plurality of equalization coefficients, each of the plurality of equalization coefficients being associated with different communication channel characteristics; equalize the processed received modulated signal on the communication channel using the selected equalizer; and detect the equalized received modulated signal.

FIELD OF THE INVENTION

The field of this invention relates to electronic devices such ascommunication units, integrated circuits, and methods for equalizationand clustering.

BACKGROUND OF THE INVENTION

Near field communications (NFC) is a set of protocols that enable, forexample, smartphones and other devices to establish radio communicationswith each other by either touching the devices together, or bringingthem into close proximity, say to a distance of typically 10 cm or less.NFC always involves an initiator device and a target device; theinitiator device actively generates a radio frequency (RF) field thatcan power a passive target device. This enables NFC target devices totake very simple form factors, such as tags, stickers, key fobs, orcards that do not require relatively large power supplies. NFCpeer-to-peer communication is possible, provided both devices arepowered.

Thus, in order to support near field communications, NFC devices fallinto two main areas: NFC tags and NFC readers/writers. NFC tags oftensecurely store personal contacts, such as debit and credit cardinformation, loyalty program data, PINs, and networking contacts, amongother information. NFC tags contain data and are typically read-only,but in some instances may be re-writable. NFC tags can be custom-encodedby their manufacturers, or they can be configured in accordance withspecifications provided by a relevant industry association.

NFC readers/writers are typically NFC-enabled devices configured to readinformation stored on inexpensive NFC tags embedded in, say, labels orsmart posters. Both NFC tags and NFC readers/writers are known to haveinterchangeable functionality and similar (or the same) components andcircuits. As such, an NFC device may often function as either a NFC tagor a NFC reader/writer.

One known problem in the provision of NFC-capable devices is the abilityof such devices being able to equalize high-data rate signals (e.g. datarates of greater than 848 kbps), as lower data rates do not requireequalization. For example, today's RF-ID systems use a 1-bit-per-symbolamplitude-shift-keying (ASK) modulation with maximum potential data ratelimited to 6.78 Mbps. However, some companies are proposing schemes toovercome these limitations and reach data rates up to 20.34 Mbps andmore. Furthermore, due to the high coupling requirements of a NFCsystem, and the effects on the coupling due to varying channelcharacteristics, high-quality (‘Q’) matching networks are required. Ifhigh-quality (‘Q’) matching networks are used, inter-symbol interference(ISI) of the transferred data may degrade the bit error rate (BER)performance of the NFC link down to more than 0.01%.

Additionally, it is problematic to equalize the high-data rate signalsunder normal operating constraints, such as: low computationalcomplexity, minimum convergence time and ensuring a high guarantee ofconvergence. A typical NFC link will also have to cope with differentcommunication channel types, with no loopback schemes or trainingsequences being available to be used.

FIG. 1 illustrates a known block diagram of a NFC link showing both anuplink communication path 100 and a downlink communication path 150 andthe types of signals encountered. In the first uplink communication path100 load (amplitude) modulation 122, 124 is employed by the NFC devices.A NFC reader 104 instigates a sinusoidal waveform 110 into a radiatedfield 106, which is looped back to the NFC reader 104 circuitry. A tag102 varies the impedance in the radiated field 106 by switching ON/OFF aresistor/capacitor (load) 108. In this manner, binary data is encodedonto the sinusoidal waveform 110 as impedance variation and results inmodulation of the sinusoidal waveform 120 being returned to the NFCreader 104. In such NFC systems the modulation index can be <1%.

In the second downlink communication path 150, waveform modulation isemployed. A NFC reader 154 instigates a sinusoidal waveform 172 into aradiated field 156 to be received by a tag 152. The data is directlymixed with carrier, or multiplied with a sub-carrier before mixing withthe carrier. In this manner, encoded binary data may be recovered. Insuch NFC architectures a minimum modulation index can be of the order of8%.

Furthermore, in a number of applications, where the communicationchannel does not exhibit flat fading, the load modulation NFC devicesmay create inter-symbol interference (ISI) when used with high symbolrates. The NFC channel characteristics are shown in the graph 180, whichillustrates two poles in the NFC frequency response. A first pole 182 isdetermined by NFC reader 104 circuitry (typically with a 1-2 MHzvariation as shown), with a second pole 184 determined by the NFC tag102 (with a 3-7 MHz variation (not shown)).

With such load modulation and waveform modulation techniques, a timingreference and accurate processing of the modulated signals is requiredin order to correctly recover and demodulate the data. In typicalcommunication techniques, a timing reference can be provided by using areliable training sequence at the transmitter for the receiver to lockon to.

Alternatively, or for high data rate applications, an equalizationtechnique may be used. As no loopback path may exist in an NFC system,because such systems need to be inherently of low complexity, such anequalization path needs to use blind estimation. Blind estimationtechniques do not require a training sequence, as known to those skilledin the art. However, blind estimation techniques introduce problems,such as an increased convergence time due to requiring thousands of bitsto achieve convergence, which increases the system's bufferingrequirements and latency.

US 2013/0064271 A1, by R. C. H. Van de Beek, M. Ciacci, and titled“Adaptive equalizer and/or antenna tuning”, describes a loopbacktraining approach whereby a loopback signal is used as training foradaptive pre-equalization. Notably, in order to provide a reliableestimation of the channel in the loopback path, which is used astraining for an adaptive pre-equalizer, each channel has its ownequalizer. However, in this loopback training approach, the loopbackchannel is different from the signal channel, thereby introducing errorsand inaccuracies. Additionally, loopback training approach requires morethan one mixer, thereby adding to the cost and complexity.

Thus, there is a general need for improved concepts to equalize data,and particularly for equalizing data in very high bit rate (VHBR) nearfield communications (NFC).

SUMMARY OF THE INVENTION

Accordingly, the invention seeks to mitigate, alleviate or eliminate oneor more of the above mentioned disadvantages, either singly or in anycombination. Aspects of the invention provide a wireless communicationunit, an integrated circuit and a method therefore, as described in theappended claims.

According to a first aspect of the invention, there is described anelectronic device for a wireless communication system. The electronicdevice comprising: a receiver configured to receive a modulated signalon a communication channel; and a processor, coupled to the receiver andconfigured to: process the received modulated signal; identify acommunication channel characteristic based on the processed receivedmodulated signal; select an equalizer having a first set of equalizationcoefficients based on the identified communication channelcharacteristic, wherein the first set of equalization coefficients isselected from a plurality of equalization coefficients, each of theplurality of equalization coefficients being associated with differentcommunication channel characteristics; equalize the processed receivedmodulated signal on the communication channel using the selectedequalizer; and detect the equalized received modulated signal.

In this manner, a similar channel characteristic nature across multiplecommunication channels may be exploited by using an equalizer that issuited for equalizing that channel or applying one or more equalizercoefficients to a generic equalizer for equalizing that channel.

According to an optional example, the processor may be configured toequalize a received near field communication, NFC, modulated signal byestimating equalization coefficients using a blind equalizationalgorithm based on the identified communication channel characteristic.

According to an optional example, each equalizer from the plurality ofgeneric equalizers may be configured to equalize a channel setexhibiting a particular communication channel characteristic.

According to an optional example, a plurality of similar communicationchannels exhibiting a particular communication channel characteristicmay have been previously clustered into a channel set.

According to an optional example, the processor may be configured todetermine a channel shape from the modulated signal received on at leastthe communication channel and select an equalizer associated with acluster of communication channels exhibiting a similar channel shape tothe determined channel shape. According to an optional example, thedetermined channel shape may be based on at least one from a group of:an estimate of an average shape of a received distribution of signals onthe communication channel, an estimate of a mid-point shape of areceived distribution of signals on the communication channel.

According to an optional example, the processor may be configured toselect an equalizer based on the identified communication channelcharacteristic using an optimality criterion that minimizes inter-symbolinterference for channel responses for each of the channel set clusters.

According to an optional example, the processor may be configured todetermine whether the identified communication channel characteristic iswithin a threshold of being similar to a pre-determined communicationchannel characteristic and selects an equalizer based thereon. Theprocessor may also be configured to calculate a bit error rate (BER) orframe error rate (FER) of the received signal such that the processorselects the equalizer based on the BER or FER of the received signal.

According to an optional example the processor may be further configuredto perform a cyclic redundancy check (CRC) on each generic equalizeroutput and select an equalizer output to detect based on the CRC.

According to an optional example, the processor may be furtherconfigured to compute a constant modulus error at the generic equalizeroutput and select an equalizer output to detect based on the constantmodulus error.

According to an optional example, the plurality of equalizers may beconfigured to apply at least one respective equalizer coefficient basedon at least one pre-calibrated communication channel characteristic.

According to a second aspect of the invention, an integrated circuit fora wireless communication system is described. The integrated circuitcomprises a processor configured to: receive a modulated signal on acommunication channel; process the received modulated signal; identify acommunication channel characteristic based on the processed receivedmodulated signal; select an equalizer having a first set of equalizationcoefficients based on the identified communication channelcharacteristic, wherein the first set of equalization coefficients isselected from a plurality of equalization coefficients, each of theplurality of equalization coefficients being associated with differentcommunication channel characteristics; equalize the processed receivedmodulated signal on the communication channel using the selectedequalizer; and detect the equalized received modulated signal.

According to a third aspect of the invention, a method for equalizing asignal in a wireless communication system is described. The methodcomprises: receiving a modulated signal on a communication channel;processing the received modulated signal; identifying a communicationchannel characteristic based on the processed received modulated signal;selecting an equalizer having a first set of equalization coefficientsbased on the identified communication channel characteristic, whereinthe first set of equalization coefficients is selected from a pluralityof equalization coefficients, each of the plurality of equalizationcoefficients being associated with different communication channelcharacteristics; equalizing the processed received modulated signal onthe communication channel using the selected equalizer; and detectingthe equalized received modulated signal.

According to a fourth aspect of the invention, a near fieldcommunication, NFC, system comprising a NFC tag in communication with aNFC electronic device is described, The NFC electronic device comprises:a receiver configured to receive a modulated signal on a NFCcommunication channel; and a processor, coupled to the receiver andconfigured to: process the received modulated signal; identify a NFCcommunication channel characteristic based on the processed receivedmodulated signal; select an equalizer having a first set of equalizationcoefficients based on the identified communication channelcharacteristic, wherein the first set of equalization coefficients isselected from a plurality of equalization coefficients, each of theplurality of equalization coefficients being associated with differentcommunication channel characteristics; equalize the processed receivedmodulated signal on the NFC communication channel using the selectedequalizer; and detect the equalized received modulated signal.

According to a fifth aspect of the invention, a processor for a computerfor clustering communication channel characteristics to equalize asignal is described. The processor is configured to: process signalsreceived on a plurality of communication channels; identify a range ofvalues of at least one communication channel characteristic from signalsreceived on the plurality of communication channels; cluster thosechannels exhibiting the identified range of values into a plurality ofchannel sets; select at least one equalizer coefficient for each of thechannel set clusters; and apply a plurality of different equalizercoefficients to a respective plurality of equalizers based on the rangeof values of the at least one communication channel characteristic.

In this manner, a generic equalizer having one or more equalizationcoefficients may be allocated to equalize signals from each of a clusterof similar communication channels, for example to use when detectingvery high bit rate (VHBR) communication in near field communications(NFC). Furthermore, in this manner, a cluster may be formed such thatone equalizer provides acceptable performance for every channel in thecluster. Thereafter, for example, a classification system may determinewhether signals received on a current channel may belong to any one ofthe known channel clusters, and equalize the signals accordingly byapplying at least one respective equalizer coefficient(s) associatedwith the known channel cluster.

According to an optional example, the at least one communication channelcharacteristic may comprise a varying channel shape and wherein theprocessor may be configured to cluster communication channels exhibitingsimilar channel shapes into a particular channel set.

According to an optional example, the processor may be configured tocompute a bit error rate (BER) or frame error rate (FER) of the signalsreceived on the plurality of communication channels and configured tocluster communication channels exhibiting similar BER or FER into aparticular channel set.

According to an optional example, the processor may be configured tocluster communication channel characteristics to equalize a signal inone from a group of: in a laboratory, on-chip in an electronic device'sintegrated circuit that comprises the processor.

According to a sixth aspect of the invention, a method for clusteringcommunication channel characteristics to equalize a signal in a wirelesscommunication system is described. The method comprises: processingsignals received on a plurality of communication channels; identifying arange of values of at least one communication channel characteristicfrom signals received on the plurality of communication channels;clustering those channels exhibiting the identified range of values intoa plurality of channel sets; selecting at least one equalizercoefficient for each of the channel set clusters; and applying aplurality of different equalizer coefficients to a respective pluralityof equalizers based on the range of values of the at least onecommunication channel characteristic.

These and other aspects of the invention will be apparent from, andelucidated with reference to, the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details, aspects and embodiments of the invention will bedescribed, by way of example only, with reference to the drawings. Inthe drawings, like reference numbers are used to identify like orfunctionally similar elements. Elements in the FIGs are illustrated forsimplicity and clarity and have not necessarily been drawn to scale.

FIG. 1 illustrates a known block diagram of a NFC uplink and downlinkcommunication link.

FIG. 2 illustrates an NFC communication device comprising a genericequalizer according to a first example embodiment of the presentinvention.

FIG. 3 illustrates a first example flowchart for equalizing very highbit rate (VHBR) near field communications (NFC), according to a firstexample embodiment of the present invention.

FIG. 4 illustrates a second example of a NFC communication deviceconfigured according to a second example embodiment of the presentinvention.

FIG. 5 illustrates a second example flowchart for generating clusters ofsimilar channel sets, for example each comprising generic equalizers touse when detecting very high bit rate (VHBR) near field communications(NFC), according to examples of the present invention.

FIG. 6 illustrates a third example of a NFC communication deviceconfigured according to a third example embodiment of the presentinvention.

FIG. 7 illustrates a third example flowchart for selecting an outputfrom one of a cluster of classified equalizers to use in detecting veryhigh bit rate (VHBR) communication in near field communications (NFC),according to examples of the present invention.

DETAILED DESCRIPTION

Although examples of the invention are described with reference to anear field communication link, with corresponding communication units,integrated circuits and methods of equalization, it is envisaged thatthe concepts described herein may be embodied in any scenario orcommunication system where multiple communication channels exhibitingsimilar channel characteristics may be found (referred hereafter as‘channel sets’), such that the similar channel characteristic nature maybe exploited. As such, the described embodiment of a near fieldcommunication link is only one such envisaged application for theconcepts described herein.

Some examples of the invention provide an NFC device, and an integratedcircuit for an NFC device, that provide equalization coefficients, forexample for high data rate ISI scenarios. In some example embodiments,the proposed equalization technique requires no training sequence andprovides a fast estimation time. In some examples, a similarity betweensets of channel shapes is used to consolidate equalizers in a blindequalization technique.

In some examples, a pre-calibrated equalization scheme based channelinformation for NFC is described. Here, the pre-calibrated equalizationscheme employs coefficients that are estimated based on an availablechannel set. If the given channel set has highly varying channel shapes,one example embodiment of the invention proposes to group these intosubsets of similar shapes, and thereafter estimate equalizercoefficients to be applied to a generic equalizer for each channel set.

In contrast to known techniques, examples of the invention do notrequire any training during normal operation. Furthermore, in contrastto known techniques, examples of the invention do not suffer fromlatency to the same degree, as no real-time computation is necessary.

Furthermore, because the illustrated examples of the present inventionmay for the most part, be implemented using electronic components andcircuits known to those skilled in the art, details will not beexplained in any greater extent than that considered necessary asillustrated below, for the understanding and appreciation of theunderlying concepts of the present invention and in order not to confuseor distract from the teachings of the present invention.

Referring to FIG. 2, there is illustrated an example of a simplifiedblock diagram of part of an electronic device adapted to support theinventive concepts of an example of the present invention. FIG. 2illustrates a NFC communication system 200 comprising a NFCcommunication link. Electronic devices, in the context of theillustrated example of the invention, include an NFC reader circuit 210and a tag 202. Again, in an uplink communication path, load modulationis employed, whereby NFC reader circuitry 210 instigates a sinusoidalwaveform into a radiated field 204, which is looped back to the NFCreader circuit 210. The tag 202 varies the impedance in the radiatedfield 204, for example by switching ‘ON’/‘OFF’ a resistor/capacitor load(not shown). In this manner, binary data is encoded as impedancevariation, and results in modulation of the sinusoidal waveform beingreturned to the NFC reader circuitry 210 from the tag 202. In thisexample, the NFC reader circuitry 210 comprises an integrated circuit211 that in some examples comprises a reader front end 212 that isarranged to capture the returned modulated sinusoidal waveform and aprocessor 213, such as a digital signal processor. The reader front end212 comprises at least a down-conversion mixer and an analog-to-digitalconverter to output a digital signal to be equalized.

The reader front end 212 provides a digital signal 214 to processor 213(that comprises in hardware, firmware or software) a generic equalizer216, which is configured to produce an equalized bit stream output 218that is input to a detector. In the context of the present invention, ageneric equalizer may comprises a processor that is capable ofperforming an equalizer function on a received signal where theequalizer coefficients, as applied to equalizer taps, are dynamicallyprogrammable. In this example, the detector is a binary phase shiftkeyed (BPSK) detector 220.

In some examples of the invention, the generic equalizer 216 may useprior channel knowledge in order to estimate suitable equalizercoefficients for the taps that sufficiently mitigate inter-symbolinterference (ISI) for a given set of ‘similar’ channels. In particular,examples of the invention provide equalization for high data rate ISIscenarios whereby, given a known set of channel responses (for exampleclosely-shaped or otherwise similar in some sense), a ‘generic’equalizer is configured such that equalizer taps are selected in orderto mitigate ISI for the set of channel responses.

In some examples of the invention, any from a number of genericequalizer estimation methods may be employed. In a first example, it isenvisaged that generic equalizer 216 may be a form of a Finite ImpulseResponse (FIR) filter, with equalizer tap settings that are set foroperating irrespective of channel characteristics. In one example, theequalizer tap setting (sometimes referred to as coefficients) may beestimated during an offline factory calibration process. In someexamples, the estimated equalizer tap settings (coefficients) may bepermanently stored on the chip.

In some examples of the invention, the generic equalizer 216 may beconfigured to estimate an ‘average’ or ‘mid-point’ shape of the receiveddistribution of signals. The corresponding equalizer taps may then beset based on such an estimate. In a second example, generic equalizer216 may be configured to use an optimality criterion that minimizes ISIfor the given set of channel responses.

Referring now to FIG. 3, a flowchart 300 illustrates one exampleprocessing operation for equalizing very high bit rate (VHBR)communication in near field communications (NFC), according to examplesof the present invention, say for generic equalizer estimation 216 ofFIG. 2. FIG. 3 illustrates an example flowchart to generate a pluralityof equalizers based on the determined channel characteristic. FIG. 3commences with a NFC communication being initiated in 302. In thisexample, data is received from a tag in 304, and the data processed in306, for example by performing a channel impulse response on the datareceived for that particular communication channel. At 308, a processoranalyses the data to select an equalizer having, say, a first set ofequalization coefficients based on the identified communication channelcharacteristic. The first set of equalization coefficients is selectedfrom a plurality of (e.g. sets of) equalization coefficients, each ofthe plurality of equalization coefficients being associated withdifferent communication channel characteristics.

In one example, the processor may be configured to estimate an ‘average’or ‘mid-point’ shape of the received distribution of signals. In thisregard, a collated set of a received distribution of signals may wellfollow a known bell-shaped curve. Thus, in this example, the processormay be configured to estimate one or more aspects of the receiveddistribution of signals to determine if they substantially follow apre-stored bell-shaped curve. Such a determination may includeestimating an average (e.g. mean, or median) from all or a subset of thereceived distribution of signals, which may or may not be the mid-pointof a bell-curve. Alternatively, or additionally, such a determinationmay include estimating a mid-point of a bell-curve for the receiveddistribution of signals, for example by looking at the middle 5%, 10%,20, or 40% of distributed samples. In another example, a suitablechannel set may be a channel that exhibits channel characteristicssimilar to another channel. As a consequence, the two channels may beconsidered as being substantially equivalent in terms of how thechannels affect data that is passed there through, and thereby beassigned to the same channel set. Based on the determined channel set,the processor applies a particular set of equalization coefficients toone or more generic equalizers in 310. Once the channel set in the NFCsystem has been determined, and suitable equalization coefficientsapplied to one or more generic equalizers, the equalized data isdetected in 312.

In this manner, using a generic equalizer, no training sequence isrequired and a fast estimation time can be achieved using the priorchannel knowledge that associates the channel with a channel set ofchannels exhibiting similar characteristics.

However, if a given set of channels has a large variation in Quality (Q)factors, the generic equalizer may not reduce any ISI to the levelsdesired. Therefore, a further example of the invention proposes toclassify a given set of channel responses into subsets, each containingsimilarly-shaped channel responses. Thereafter, examples of theinvention propose to obtain a generic equalizer for each subset ofsimilarly-shaped channel responses. In other examples, for differentchannel types, one example of the invention proposes to classify thechannels into sets based on similarity, and obtain a generic equalizerfor each set.

A first example receiver design that employs multiple parallel receiverchains is described in FIG. 4, where equalizer coefficients areallocated to multiple parallel generic equalizers, for example on a perchannel set basis. In employing multiple parallel receiver chains, thefirst example receiver design is able to select and apply respectiveequalizer coefficients without exhibiting any latency. In contrast, in asecond example receiver design illustrated in FIG. 6, a blind algorithmmay be used to determine the channel set, and thereby selected equalizercoefficients. The second example receiver design that utilizes a blindalgorithm to select equalizer coefficients exhibits some latency.However, this approach requires less power and hardware.

Referring now to FIG. 4, there is illustrated an example of a simplifiedblock diagram of part of an electronic device adapted to support theinventive concepts of an example of the present invention. FIG. 4illustrates an NFC communication system 400 comprising a NFCcommunication link and the electronic device, in the context of theillustrated example of the invention, is an NFC reader circuitry 410 anda tag 402 according to examples of the present invention. In thisexample, the NFC reader circuitry 410 comprises an integrated circuit411 that in some examples comprises a reader front end 412 that isarranged to capture a returned modulated sinusoidal waveform and aprocessor 413, such as a digital signal processor. The reader front end412 provides multiple output signals 414, 415, to processor 413 thatsupports multiple receiver chains, with two chains shown for simplicitypurposes only. In this example, therefore, there is no latency in theequalization and demodulating/decoding process. The multiple receiverchains comprise multiple generic equalizers 416, 417 configured toreceive and equalize respective digital output signals 414, 415. In thisexample, each of the multiple generic equalizers 416, 417 is associatedwith a particular channel set. As such, each generic equalizer 416, 417,is configured with equalization coefficients that can equalize signalscarried by a cluster of similar channels. Hence, a plurality ofdifferent equalizer coefficients are applied to a respective pluralityof equalizers 416, 417, based on a range of values of the at least onecommunication channel characteristic. Thus, each generic equalizer 416,417, perform generic equalization for cluster-n with respective genericequalization coefficients and produces respective equalized bit streamoutputs 418, 419. Thus, in some examples, a cluster may be formed suchthat one equalizer provides acceptable performance for every channel inthe cluster. The respective equalized bit stream outputs 418, 419 areinput to multiple respective detectors in separate detector chains,which in this example are multiple binary phase shift keyed detectors420, 421. The digital detector outputs 422, 423 are then input tomultiple respective error correction circuits 424, 425, which in thisexample include cyclic redundancy checking (CRC) circuits 424, 425. Ifthe channel carrying the data belongs to cluster-n, the n-th CRC willpass a given threshold. After each of the CRC circuits 424, 425 performsa CRC check on the received equalized data, the CRC output that passes agiven threshold, perhaps by the largest margin, will be selected. Thefunctionality in the processor 413 may be implemented as one or more of:hardware, firmware or software.

Advantageously, in this example and as a consequence of there beingmultiple receiver chains in parallel, no latency results and thereforeno buffers are needed. However, in this example and as a result ofproviding multiple parallel receiver chains, slightly more hardware isrequired and more power is used.

FIG. 5 illustrates a second example flowchart for generating a clusterof similar communication channels, such that a generic equalizer havingone or more equalization coefficients may be allocated to equalize thatcluster of similar communication channels, for example to use whendetecting very high bit rate (VHBR) communication in near fieldcommunications (NFC), according to examples of the present invention. Inone example, the cluster generation procedure may be performed in alaboratory using, say an external computer comprising a processor. In afurther example, it is envisaged that the communication channel clusterclassification system procedure may be performed within the device'sprocessor or integrated circuit. FIG. 5 commences with a NFCcommunication being initiated in 502. In this example, data is receivedfrom a tag in 504, and the data processed in 506, for example includingoptionally measuring and recording bit error rate (or similar)measurements to indicate the state of the communication channel. At 508,a processor analyses the data to identify one or more channelcharacteristics, such as one or more of: a bit error rate (BER) or frameerror rate (FER) of the received signal, a cyclic redundancy check (CRC)on each generic equalizer output, a constant modulus error at thegeneric equalizer output, based on the processed received data.

In this example flowchart, a determination is then made as to whetherthe processed channel data relates to the last channel to be processed,in 510. If it is determined that the processed channel data does notrelate to the last channel to be processed, in 510, the process moves tothe next channel in 512 and loops to 504 and repeats. If it isdetermined that the processed channel data does relate to the lastchannel to be processed, in 510, the processor then clusters channelsthat exhibit similar channel characteristics in 514. In one example,similar channels are clustered together to form a channel set, forexample based on an identified range of values following their measuredBER or FER performance.

In this manner, and thereafter based on a receiving data on a channelthat is similar to a determined channel set, a processor in theelectronic device, such as an NFC reader, is able to apply a particularset of equalization coefficients to one or more generic equalizers toequalize the received data prior to detection.

Referring to FIG. 6, there is illustrated a yet further example of asimplified block diagram of part of an electronic device adapted tosupport the inventive concepts of an example of the present invention.FIG. 6 illustrates an NFC communication link 600 and the electronicdevice, in the context of the illustrated example of the invention, isan NFC reader circuitry 610 and a tag 602 according to examples of thepresent invention. In this example, the NFC reader circuitry 610comprises an integrated circuit 611 in this example and adopts aclassification system to improve the equalization process. In oneexample, the communication channel cluster classification systemprocedure may be performed in a laboratory using, say an externalcomputer comprising a processor. In a further example, it is envisagedthat the communication channel cluster classification system proceduremay be performed within the device's processor or integrated circuit. Inone example, the classification system may divide the entire channel setinto two or more clusters, whereby equalization coefficients areobtained for each cluster. In this scenario, a generic equalizer may beemployed for each of the plurality of subsets. Cluster identification isthe process of identifying the cluster to which the channel belongs to.

In this example, the NFC reader circuitry 610 comprises a reader frontend 612 that is arranged to capture a returned modulated sinusoidalwaveform and a processor 613, such as a digital signal processor. Thereader front end 612 provides multiple output signals 614, 615, toprocessor 613 that supports multiple generic equalizers 616, 617configured to receive and equalize respective digital output signals614, 615, and produce respective equalized bit stream outputs 618, 619.Generic equalizer coefficients for various clusters are available at thereceiver.

The respective equalized bit stream outputs 618, 619 are input into aclassification system 630 to improve the equalization process. In oneexample, the classification system 630 may classify a given set into aplurality of subsets, whereby each subset contains similarly shapedchannels. The classification system 630 determines whether the currentchannel may belong to any one of the known channel clusters.Alternatively, the output of each of the generic equalizers 616, 617 isassessed with the outputs varying dependent upon the equalizercoefficients employed in the respective generic equalizers 616, 617. Theclassification system 630 then determined the correct path, e.g. channelset and equalizer coefficients to use when detecting the receive signalbased on a calculation, for example analyzing the equalized data toidentify a constant modulus error. Thereafter, the classification system630 selects one of the multiple equalizer coefficient sets to use basedon the identified channel cluster and forwards the selected equalizercoefficient set for that channel cluster to a single detector, e.g. BPSKdetector 620. The functionality in the processor 613 may be implementedas one or more of: hardware, firmware or software.

Advantageously, in this example of FIG. 6, only one detector chain isneeded. As such, this approach uses less power consumption. However, inthis example of FIG. 6, a certain number of samples from the multiplegeneric equalizer sets 616, 617, have to be obtained before theclassification system can determine whether the current channel maybelong to any one of the known channel clusters. The requirement to usemultiple generic equalizer sets 616, 617, without duplicating detectionand error checking for each path, introduces latency, as buffering ofthe data is necessary.

In this manner, a blind algorithm is used to select the equalizercoefficient set.

FIG. 7 illustrates a third example flowchart for selecting an outputfrom one of a cluster of channel sets, each having a generic equalizerconfigured to equalize a received data signal carried by a particularchannel type, to use in detecting very high bit rate (VHBR)communication in near field communications (NFC), according to examplesof the present invention. FIG. 7 commences with a NFC communicationbeing initiated in 702. In this example, data is received from a tag in704, and the data processed in 706, for example including routing theprocessed data through multiple generic equalizers with differentequalization coefficients, configured based on different channel sets.At 708, a processor is configured to select a particular channel set(and thereby equalization coefficients) from a cluster of channel sets.In some examples, the processor is configured to select a particularchannel set based on a CRC value of the processed data or compute aconstant modulus error at the generic equalizer output and select anequalizer output to detect based on the constant modulus error.Thereafter, based on data received on a channel that is similar to adetermined and selected channel set, a processor is able to applydetection to the selected equalized data in 712.

In the forgoing specification, an invention has been described withreference to specific illustrated examples. It will, however, be evidentthat various modifications and changes may be made therein withoutdeparting from the scope of the invention as set forth in the appendedclaims.

The connections as discussed herein may be any type of connectionssuitable to transfer signals from or to the respective nodes, units ordevices, for example via intermediary components. Accordingly, unlessimplied or stated otherwise, the connections may for example be directconnections or indirect connections. The connections may be illustratedor described in reference to being a single connection, a plurality ofconnections, unidirectional connections or bidirectional connections.However, different illustrated examples may vary the implementation ofthe connections. For example, separate unidirectional connections may beused rather than bidirectional connections and vice versa. Also,plurality of connections may be replaced with a single connection thattransfers multiple signals serially or in a time multiplexed manner.Likewise, single connections carrying multiple signals may be separatedout into various different connections carrying subsets of thesesignals. Therefore, many options exist for transferring signals.

Although specific conductivity types or polarity of potentials have beendescribed in the examples, it will be appreciated that conductivitytypes and polarities of potentials may be reversed.

Any arrangement of components to achieve the same functionality iseffectively ‘associated such that the desired functionality is achieved.Hence, any two components herein combined to achieve a particularfunctionality can be ‘associated with’ each other such that the desiredfunctionality is achieved, irrespective of architectures or intermediarycomponents. Likewise, two components so associated can also be viewed asbeing ‘operably connected’, or ‘operably coupled’ to each other toachieve the desired functionality.

Furthermore, those skilled in the art will recognise that boundariesbetween the above described operations are merely illustrative. Themultiple operations may be combined into a single operation, a singleoperation may be distributed in additional operations and operations maybe executed at least partially overlapping in time. Moreover,alternative embodiments may include multiple instances of a particularoperation, and the order of operations may be altered in various otherembodiments.

Furthermore, the illustrated examples may be implemented as circuitrylocated in a single integrated circuit or within the same device.Alternatively, the illustrated examples may be implemented as any numberof separate integrated circuits or separate devices interconnected witheach other in a suitable manner. However, other modifications,variations and alternatives are also possible. The specifications anddrawings are, accordingly, to be regarded in an illustrative rather thanin a restrictive sense.

In some examples, an integrated circuit for a wireless communicationsystem is described wherein the integrated circuit comprises a processorconfigured to: receive a modulated signal on a communication channel;process the received modulated signal; identify a communication channelcharacteristic based on the processed received modulated signal; selectan equalizer having a first set of equalization coefficients based onthe identified communication channel characteristic, wherein the firstset of equalization coefficients is selected from a plurality ofequalization coefficients, each of the plurality of equalizationcoefficients being associated with different communication channelcharacteristics; equalize the processed received modulated signal on thecommunication channel using the selected equalizer; and detect theequalized received modulated signal.

In this manner, a generic equalizer having one or more equalizationcoefficients may be allocated to equalize signals from each of a clusterof similar communication channels, for example to use when detectingvery high bit rate (VHBR) communication in near field communications(NFC). Furthermore, in this manner, a cluster may be formed such thatone equalizer provides acceptable performance for every channel in thecluster. Thereafter, for example, a classification system may determinewhether signals received on a current channel may belong to any one ofthe known channel clusters, and equalize the signals accordingly byapplying at least one respective equalizer coefficient(s) associatedwith the known channel cluster.

In some examples, processor (which may be implemented on an integratedcircuit) is described wherein the processor is configured to: processsignals received on a plurality of communication channels; identify arange of values of at least one communication channel characteristicfrom signals received on the plurality of communication channels;cluster those channels exhibiting the identified range of values into aplurality of channel sets; select at least one equalizer coefficient foreach of the channel set clusters; and apply a plurality of differentequalizer coefficients to a respective plurality of equalizers based onthe range of values of the at least one communication channelcharacteristic.

It will be appreciated that, for clarity purposes, the above descriptionhas described embodiments of the invention with reference to differentfunctional units and processors. However, it will be apparent that anysuitable distribution of functionality between different functionalunits or processors, for example with respect to the equalizers,detectors, cyclic redundancy check circuits or components, etc., may beused without detracting from the invention. Hence, references tospecific functional units are only to be seen as references to suitablemeans for providing the described functionality, rather than indicativeof a strict logical or physical structure or organization.

Although the present invention has been described in connection withsome embodiments, it is not intended to be limited to the specific formset forth herein. Rather, the scope of the present invention is limitedonly by the accompanying claims. Additionally, although a feature mayappear to be described in connection with particular embodiments, oneskilled in the art would recognize that various features of thedescribed embodiments may be combined in accordance with the invention.In the claims, the term ‘comprising’ does not exclude the presence ofother elements or steps.

Furthermore, although individually listed, a plurality of means,elements or method steps may be implemented by, for example, a singleunit or processor. Additionally, although individual features may beincluded in different claims, these may possibly be advantageouslycombined, and the inclusion in different claims does not imply that acombination of features is not feasible and/or advantageous. Also, theinclusion of a feature in one category of claims does not imply alimitation to this category, but rather indicates that the feature isequally applicable to other claim categories, as appropriate.

Furthermore, the order of features in the claims does not imply anyspecific order in which the features must be performed and in particularthe order of individual steps in a method claim does not imply that thesteps must be performed in this order. Rather, the steps may beperformed in any suitable order. In addition, singular references do notexclude a plurality. Thus, references to ‘a’, ‘an’, ‘first’, ‘second’,etc. do not preclude a plurality.

Thus, an improved electronic device, such as a communication unit,integrated circuit, processor for a computer and equalization method andmethod for clustering communication channels for equalization have beendescribed, for example in equalizing very high bit rate (VHBR)communication in near field communications (NFC), wherein theaforementioned disadvantages with prior art arrangements have beensubstantially alleviated.

We claim:
 1. An electronic device for a wireless communication system,the electronic device comprising: a receiver configured to receive amodulated signal on a communication channel; and a processor, coupled tothe receiver and configured to: process the received modulated signal;identify a communication channel characteristic based on the processedreceived modulated signal; select an equalizer having a first set ofequalization coefficients based on the identified communication channelcharacteristic, wherein the first set of equalization coefficients isselected from a plurality of equalization coefficients, each of theplurality of equalization coefficients being associated with differentcommunication channel characteristics; equalize the processed receivedmodulated signal on the communication channel using the selectedequalizer; and detect the equalized received modulated signal.
 2. Theelectronic device of claim 1, wherein the processor is configured toequalize a received near field communication, NFC, modulated signal byestimating equalization coefficients using a blind equalizationalgorithm based on the identified communication channel characteristic.3. The electronic device of claim 1, wherein each set of equalizationcoefficients from the plurality of equalization coefficients isconfigured to equalize a plurality of communication channels exhibitinga particular communication channel characteristic.
 4. The electronicdevice of claim 3, wherein the plurality of communication channelsexhibiting the particular communication channel characteristic have beenpreviously clustered into a channel set.
 5. The electronic device ofclaim 1, wherein the processor is configured to determine a channelshape from the modulated signal received on at least the communicationchannel and select an equalizer associated with a cluster ofcommunication channels exhibiting a similar channel shape to thedetermined channel shape.
 6. The electronic device of claim 5, whereinthe processor is configured to determine a channel shape based on atleast one from a group of: an estimate of an average shape of a receiveddistribution of signals on the communication channel, an estimate of amid-point shape of a received distribution of signals on thecommunication channel.
 7. The electronic device of claim 5, wherein theprocessor is configured to select an equalizer based on the identifiedcommunication channel characteristic using an optimality criterion thatminimizes inter-symbol interference for channel responses for each ofthe channel set clusters.
 8. The electronic device of claim 1, whereinthe processor is configured to determine whether the identifiedcommunication channel characteristic is within a threshold of beingsimilar to a pre-determined communication channel characteristic andselects an equalizer based thereon.
 9. The electronic device of claim 1,wherein the processor is configured to calculate a bit error rate, BER,or frame error rate, FER, of the received signal such that the processorselects the equalizer based on the BER or FER of the received signal.10. The electronic device of claim 1, wherein the processor is furtherconfigured to perform a cyclic redundancy check, CRC, on each genericequalizer output and select an equalizer output to detect based on theCRC.
 11. The electronic device of claim 1, wherein the processor isfurther configured to compute a constant modulus error at the genericequalizer output and select an equalizer output to detect based on theconstant modulus error.
 12. The electronic device of claim 1, whereinthe plurality of equalizers are configured to apply at least onerespective equalizer coefficient based on at least one pre-calibratedcommunication channel characteristic.
 13. An integrated circuit for awireless communication system, the integrated circuit comprising aprocessor configured to: receive a modulated signal on a communicationchannel; process the received modulated signal; identify a communicationchannel characteristic based on the processed received modulated signal;select an equalizer having a first set of equalization coefficientsbased on the identified communication channel characteristic, whereinthe first set of equalization coefficients is selected from a pluralityof equalization coefficients, each of the plurality of equalizationcoefficients being associated with different communication channelcharacteristics; equalize the processed received modulated signal on thecommunication channel using the selected equalizer; and detect theequalized received modulated signal.
 14. A method for equalizing asignal in a wireless communication system, the method comprising:receiving a modulated signal on a communication channel; processing thereceived modulated signal; identifying a communication channelcharacteristic based on the processed received modulated signal;selecting an equalizer having a first set of equalization coefficientsbased on the identified communication channel characteristic, whereinthe first set of equalization coefficients is selected from a pluralityof equalization coefficients, each of the plurality of equalizationcoefficients being associated with different communication channelcharacteristics; equalizing the processed received modulated signal onthe communication channel using the selected equalizer; and detectingthe equalized received modulated signal.
 15. A near field communication,NFC, system comprising a NFC tag in communication with a NFC electronicdevice, wherein the NFC electronic device comprises: a receiverconfigured to receive a modulated signal on a NFC communication channel;and a processor, coupled to the receiver and configured to: process thereceived modulated signal; identify a NFC communication channelcharacteristic based on the processed received modulated signal; selectan equalizer having a first set of equalization coefficients based onthe identified communication channel characteristic, wherein the firstset of equalization coefficients is selected from a plurality ofequalization coefficients, each of the plurality of equalizationcoefficients being associated with different communication channelcharacteristics; equalize the processed received modulated signal on theNFC communication channel using the selected equalizer; and detect theequalized received modulated signal.
 16. A processor for a computer forclustering communication channel characteristics to equalize a signal,the processor configured to: process signals received on a plurality ofcommunication channels; identify a range of values of at least onecommunication channel characteristic from signals received on theplurality of communication channels; cluster those channels exhibitingthe identified range of values into a plurality of channel sets; selectat least one equalizer coefficient for each of the channel set clusters;and apply a plurality of different equalizer coefficients to arespective plurality of equalizers based on the range of values of theat least one communication channel characteristic.
 17. The processor ofclaim 16, wherein the at least one communication channel characteristiccomprises a varying channel shape and wherein the processor isconfigured to cluster communication channels exhibiting similar channelshapes into a particular channel set.
 18. The processor of claim 16,wherein the processor is configured to compute a bit error rate, BER, orframe error rate (FER) of the signals received on the plurality ofcommunication channels and configured to cluster communication channelsexhibiting similar BER or FER into a particular channel set.
 19. Theprocessor of claim 16, wherein the processor is configured to clustercommunication channel characteristics to equalize a signal in one from agroup of: in a laboratory, on-chip in an electronic device's integratedcircuit comprising the processor.
 20. A method for clusteringcommunication channel characteristics to equalize a signal in a wirelesscommunication system, the method comprising: processing signals receivedon a plurality of communication channels; identifying a range of valuesof at least one communication channel characteristic from signalsreceived on the plurality of communication channels; clustering thosechannels exhibiting the identified range of values into a plurality ofchannel sets; selecting at least one equalizer coefficient for each ofthe channel set clusters; and applying a plurality of differentequalizer coefficients to a respective plurality of equalizers based onthe range of values of the at least one communication channelcharacteristic.